1)
What Tzedah and Shofaros did they take?
1.
Radak: They took the provisions and Shofaros of the men who returned home, so each remaining man had a Shofar, in order to confound the enemy. Even though Tzedah is Samuch, it does not say Tzedas. We find like this, e.g. "k'Eifah Se'orim" (Rus 2:17).
2)
Why does it say that Midyan was in the valley? It already said so (verse 1)!
1.
Malbim: Now, Gid'on ascended the mountain, and Midyan was below him.